At least nine people were killed and scores injured after two commuter trains collided at high speed in southern Germany early Tuesday, officials said.
A massive rescue operation — involving more than 500 personnel and some 14 helicopters — was launched following the crash near the town of Bad Aibling in Bavaria at around 7 a.m. local time (1 a.m. ET).
German officials told a press conference two passengers were still missing more than six hours after the incident.
While police initially said 150 people were injured in the crash, that number was later revised down to 81 — including 18 people listed with "severe" injuries."
German leader Angela Merkel said she was "aghast and saddened by the grave train disaster," expressing sympathy for the victims and thanking the "tireless work" of rescuers in a statement.
Officials said it was too soon to say what may have caused the crash.
The trains were traveling around a curve at around 60 mph on a single-track route when they collided, German Transport Minister Alexander Dobrindt told reporters.
"One train more or less plowed into the other," he said, adding that the curve meant it was unlikely the train drivers saw each other.
He said the railway was equipped with a safety mechanism that should have forced the trains to automatically brake, but that it was too soon to say "what kind of effect it had in this case" and that crews were still attempting to recover the trains' black boxes.
"I just visited the crash site and it is a scary picture," Dobrindt said.
There were around 150 people in total on both trains, according to officials.
Both trains were on running on the so-called Meridian line.
"The accident is a big shock for us," said Bernd Rosenbusch, chief executive of train operator Bayerischen Oberlandbahn.
Bayerischen Oberlandbahn's technical CEO Fabian Amini said in a statement that teams "were on location quickly and were able to get a picture of the collision."
"We thank the rescue services and staff who have helped so quickly," Amini added.
All trains on the line have been suspended and replaced with bus services, according to the firm.
The crash site was in a hard-to-reach wooded area next to the river Mangall between Rosenheim and Bad Aibling. Rescue helicopters could be seen airlifting casualties away from the wreckage for treatment.
The local blood donation center based in Munich, around 30 miles away, issued a statement urging people to give blood after the "tragic train accident … increased the need of life saving blood donations."
Justice Minister Heiko Maas thanked rescue teams in a message posted on Twitter.
"Very bad news from #badaibling," he wrote. "Our thoughts are with the victims + injured."
This article first appeared on NBCNews.com.