A submarine that normally carries tourists to view the wreckage of the Titanic has disappeared off the east coast of the US.

According to that source, it is not known whether there were passengers on board the submarine and, if so, how many.

It is not clear how many people were on board at the time she went missing.

Small submersibles occasionally carry tourists and paying experts to view the Titanic wreck, the BBC reported.

Multi-day trips to the wreck cost tens of thousands of dollars, and a Titanic dive, which includes both descent and ascent, takes about eight hours.

The famous shipwreck lies 3,800 m deep at the bottom of the Atlantic Ocean, about 600 km off the coast of Newfoundland, Canada. The passenger liner, once the largest ship of its time, collided with an iceberg on its maiden voyage from Southampton to New York in 1912.

Of the 2,200 passengers and crew on board, more than 1,500 died. The Titanic has been extensively explored since the wreck was discovered in 1985.