Nigeria has levied large fines against air carriers British Airways and Virgin Atlantic for allegedly overcharging passengers for tickets.

Officials said Thursday that the Nigerian Civil Aviation Authority has fined British Airways $135 million and Virgin Atlantic $100 million.

Nigerian officials accuse the carriers of working together since 2004 to increase fuel surcharges in order to inflate ticket prices.

They say the fines follow a six-month investigation.

Both British Airways and Virgin Atlantic have denied any wrongdoing.