BERLIN, Feb 9 (Reuters) Four people were killed when two trains collided head-on in the southern German state of Bavaria today, a police spokesman said, adding about 150 people were injured, including 10 very seriously. The collision took place on a single track, he said. The cause of the accident was unclear and police said that, alongside the rescue effort, investigations were starting into establishing what had happened. The accident between two local passenger trains operated by Meridian happened at 6.48 a.m. local time (1118 IST) near Bad Aibling in the southeastern corner of Germany. Dozens of rescue teams were on site, including helicopters, and streets in the area were closed. Police will hold a news conference at 12.00 local time (1630 IST). Meridian is part of the Transdev group. Deutsche Bahn is responsible for the track. REUTERS PS NS1434