Fraud police in Nigeria have seized the passports of four top football officials sacked after the country's poor performance at the World Cup.Nigerian football has been in turmoil since the team left the competition without winning a game.The president initially banned the team from international competition, but changed his mind after pressure from the football world governing body.The officials face questions over how more than $8m (£5.2m) was spent.They have not many any formal statement about the investigation since their sacking but are fully co-operating with the authorities.The BBC's Caroline Duffield in Lagos says the Super Eagles' performance in South Africa provoked nationwide anger - and questions over where public money was going.She says the head of the special financial crimes police, Farida Waziri, is personally handling the investigation - an indication of how politically sensitive it is.Meanwhile the sacked Football Federation President, Sani Lulu, is refusing to speak to the media, our reporter says.The Lulu family say his mother was kidnapped earlier this week, and they face a ransom demand of $1.7m.Credit: BBC