Terrorism does not appear to have been a factor in the collapse of a major US bridge that fell into Baltimore harbour after a container ship crashed into it.

“There is absolutely no indication that there’s any terrorism, that this was done on purpose,” said Baltimore Police Commissioner Richard Worley.

A footage showed a 300-meter vessel hitting the Francis Scott Key Bridge, bringing the steel-built structure crashing into the Patapsco River.

The footage also appeared to show the ship going dark twice in the moments before the collision, possibly indicating some kind of power failure on board.

A huge emergency response swung into action after the collision, which happened around 1:30 am (0530 GMT), with first response vehicles crowding the shoreline.

Water temperatures were around 48 Fahrenheit (9 Celsius), narrowing the window of survivability.

Baltimore’s fire chief James Wallace said sonar had “detected the presence of vehicles” in the harbour, but declined to estimate how many.

One person was taken to hospital in “a very serious condition,” he said, adding a second person recovered from the water was uninjured.

“We may be looking for upwards of seven individuals,” he said.