Four sailings between Vancouver and Victoria were cancelled Friday after crew members were injured in an incident involving a rescue boat.

BC Ferries said two people were injured during a 6 a.m. regulatory drill, when the boat rocked and they were thrown into the water. The union that represents BC Ferries workers said the issue was a failure of the Spirit of Vancouver's davit, the crane used for lowering rescue boats.

The crew members fell into the water from a "significant height," the BC Ferry and Marine Workers Union said in a statement. The BC Ferries and the BCFMWU did not provide details on the extent of their injuries, but said they'd been taken to hospital.

"This is the second time this year there has been a substantial failure regarding rescue boats, and these incidents cause our union deep concern," provincial president Graeme Johnston said.

Two workers conducting a rescue boat drill on the Queen of Cumberland also fell into the water in April. They were seriously injured and have not been able to return to work.

BC Ferries CEO Mark Collins said he couldn't say whether the incidents were related.

"It's too early. We don't know fully what happened today, but the investigation will look into this and certainly all lessons learned will be acted upon," he said.

Investigations are also being conducted by WorkSafeBC and the Transportation Safety Board.

As a result of the incident, the 7 a.m. and 11 a.m. sailings from Swartz Bay, and the 9 a.m. and 1 p.m. sailings from Tsawwassen, have been cancelled.

Some would-be travellers who arrived to find their reservations cancelled told CTV News they'd waited hours for another sailing, as many later times were already booked up.

In a statement posted Friday morning, the company said it appreciated passengers' patience and apologized for the inconvenience.

The incident Friday is not BC Ferries' first issue on a long weekend this summer.

One of its vessels was expected to be back in service by the Canada Day weekend but the repairs were delayed and some travellers' reservations were cancelled.

There were issues with another ferry the following weekend.

Last month, Premier John Horgan acknowledged the public's calls for newer vessels at the time and added that there is a review of BC Ferries underway.

Meanwhile, customers have been paying more for the service since the end of June due to the removal of fuel rebates. Added costs vary, but it amounts to an extra 50 cents for walk-on passengers and $1.70 for vehicles on major routes.