A crash Tuesday morning between a passenger bus and cargo truck killed six people and injured at least 20 near Mexico's capital, the state-run Notimex news agency reported.

Preliminary reports indicate the bus was speeding and crashed into the back of the truck, which was carrying boxes of chicken, Notimex said.

After the 6 a.m. crash, Notimex said, the bus ended up blocking two of the three northbound lanes of the Mexico-Puebla highway. Video on CNN affiliate Televisa showed a long line of traffic backed up on the highway lanes headed toward Mexico City.

Televisa also showed chicken boxes and other debris from the crash scattered over a wide area of road and the highway shoulder.

A crane, brought in to put the bus upright and help retrieve passengers, finished its work around 7:30 a.m., Notimex said.