At least seven members of a single family were killed and another was critically injured Sunday when their packed car collided with a tractor trailer in central Colombia, police said. The collision occurred early in the day on a highway linking Bogota with the capital of central Meta province, Villavicencio, the head of the police department's Transit and Transportation Bureau, Gen. Francisco Patino, said. Patino said it appeared the accident was caused by the fact the car was speeding and overloaded with passengers, all members of the same family, including several minors. The car was carrying "four adults, an adolescent and two children," in addition to the driver, said Col. Juan Vivas, head of the Villavicencio police department. "That is a totally irresponsible act on the part of the driver." Police also found "two tied-up animals in the trunk" of the car, police said. A 10-year-old girl that was critically injured was taken to a nearby hospital for treatment. Authorities are investigating whether the driver of the tractor trailer, who was unharmed, bears any responsibility for the crash. The accident marked the first major incident of an extended three-day weekend in Colombia, as Monday is a holiday. In preparation for the increased weekend traffic, the police had increased their presence along the nation's highways with some 780, 000 patrol cars, according to official figures.