Five people were killed after a small plane crashed on a highway in Mexico, officials said.The aircraft crashed onto a highway connecting the country's capital Mexico City with the central state of Queretaro, Xinhua news agency reported on Wednesday. Gerardo Quirarte Perez, head of the State Civil Protection Agency, told reporters that the plane crashed and burnt, after the crew tried to make an emergency landing due to a mechanical failure.There was no information on where the plane was headed or took off from, or the identities of those on board.