The Nigerian president has expressed deep concern over a high number of unexplained deaths in the northern state of Kano, amid fears they could be caused by Covid-19.

President Muhammadu Buhari said a lockdown would be imposed in Kano for an additional two weeks, and that he was sending a government team to investigate.

Nigeria's Health Minister Dr Osagie Ehanire says the situation is being "monitored closely".

But following preliminary investigations the state authorities have dismissed a connection with coronavirus.

Hundreds of people are rumoured to have died in the community but no official death records are kept.

Grave diggers initially raised concerns that they were burying a higher than usual number of bodies.

Ali, a grave digger at the Abattoir Graveyard, told the BBC: "We have never seen this, since the major cholera outbreak that our parents tell us about. That was about 60 years ago."

This week, the state governor issued a statement saying the "mysterious deaths" were unrelated to coronavirus.

But after ordering a "thorough investigation into the immediate and remote causes of the deaths", announced that their preliminary findings "indicated that the deaths are not connected to the Covid-19 pandemic".

The state government said "reports from the state ministry of health has shown that most of the deaths were caused by complications arising from hypertension, diabetes, meningitis and acute malaria".

"Governor Abdullahi Umar Ganduje is earnestly waiting for the final report from the state ministry of health so as to take the necessary action."

The commercial and industrial centre of the north, Kano has become the epicentre of coronavirus in northern Nigeria. Its highly dense population is still in lockdown in an effort to contain the spread of the virus.

Don't tests show the cause of death?

State officials started testing for Covid-19 two weeks ago and one lab has had to close due to contamination. Samples are being sent to the capital, Abuja, which authorities say is causing a delay in announcing how many positive cases have been detected in the state.

Dr Sani Aliyu, who is the national co-ordinator for the presidential task force on Covid-19, says a team of five medical experts were deployed to Kano to facilitate in reopening the testing centre this week after it was fumigated.

Officials also plan to open a second lab, at Bayero University, for testing for Covid-19 from next week.

How many people have died?

It is unclear how many people have died, as the deaths causing concern are happening in the community. Deaths in many parts of Nigeria are not registered, and so for those who died outside of hospital, no records are kept.

This makes it difficult to understand how many people have died in recent weeks.

Sabitu Shaibu, the deputy head of the state task force on Covid-19, is hoping to release preliminary findings of the investigation by next week but believes that most of the rumoured 640 deaths are from natural causes and says the figure is below the average death rate for Kano.

Hospital records which provide the only death register available are thought to provide lower numbers than the real picture across the state.

Those on the investigating taskforce say they will conduct "verbal autopsies" with family members to help establish why people are dying.

If not coronavirus, what else could be going on?

Private hospitals which provide for a significant part of health provision in the region have been closed due to coronavirus fears. This could mean a lack of support for those with existing conditions who may have died as a result.

Dr Nagoma Sadiq who works at the Aminu Kano Hospital, thinks this could be behind the additional deaths, but he is also not ruling out coronavirus.

"It's shocking to most of us that the count of the dead is alarming. But it's likely due to the reduction in the number of health institutions available in the state.

"Because there are a lot of hypertensive patients, diabetic patients, asthmatic patients, cancer patients, and they don't have much access to the hospitals. The lockdown is affecting everybody.

"Our poor majority don't even have a vehicle to take them to the hospitals."

Grave digger Ali agrees, adding "some say the current situation is due to the epidemic, others say it's difficulties of life. People have so many problems in their lives and a lack of peace of mind."

However Covid-19 is known to be more dangerous for those with underlying health conditions, so it could be that the deaths are related to coronavirus. The only way to know for sure is to test for coronavirus.

Dr Sadiq also said that there was still a concern about an ongoing Lassa fever infection amongst communities. The state has had five confirmed cases and one death, according to the most recent report from the Nigerian Centre For Disease Control.

Kano currently has 77 positive cases of coronavirus with three deaths.

Authorities are urging the public not to panic.

What else did the president announce?

President Buhari announced a gradual easing of lockdown restrictions in Abuja, Lagos and neighbouring Ogun state from next Monday.

But he also said that the government would impose a curfew across the country between 20:00 and 06:00, require everyone to wear face masks in public, and stop "non-essential inter-state passenger travel".

Bans on social and religious gatherings will also remain in place.