More than 100 people have died after a petrol pipeline explosion and fire in Kenya's capital, Nairobi, police say.The blast took place in the city's Lunga Lunga industrial area, and firefighters were battling fierce flames that were threatening a nearby shanty town.The pipeline runs through a densely populated area between Nairobi's city centre and the airport.More than 80 casualties have been taken to hospitals, officials said.An ambulance service spokesman said that many of the victims were burnt beyond recognition.It is not known what caused the blast.Police and troops have cordoned off the district, where residents said an earlier leak in the pipeline had prompted many people to rush and collect leaking fuel."Then there was a loud bang, a big explosion, and smoke and fire burst up high," resident Joseph Mwego told Agence France-Presse.There have been other deaths involving people collecting leaking fuel: More than 100 people died in Molo, western Kenya, in 2009 after a fire on an overturned tanker.