LUCKNOW, India (Reuters) - At least 18 people were killed in north India after a bus collided with a milk tanker early on Wednesday, police said.

The collision on an expressway in the Unnao district of Uttar Pradesh state, about 500 km (310 miles) southeast of Delhi, also injured at least 19 people, said Arvind Chaurasia, a top district police officer.

The bus was on its way to New Delhi from the eastern state of Bihar, he said, adding that police are still verifying how many passengers were on the bus.

"Injured passenger told us that the bus driver was driving recklessly, and the incident happened when he rammed the bus into a tanker carrying milk on the expressway," he said.

(Reporting by Saurabh Sharma in Lucknow; editing by Miral Fahmy)