LONDON — British coast guards say they have detained five cruise ships after concerns about the welfare of crew members stranded by the coronavirus pandemic, some of whom have been aboard for a year.

The Maritime and Coastguard Agency says it found “a number of expired and invalid Seafarers Employment Agreements, late payment of wages and crews who had been on board for over 12 months” when it inspected the ships.

Four of the vessels — the Astoria, Astor, Columbus and Vasco da Gama — are berthed at Tilbury Docks, east of London. The fifth, the Marco Polo, is at Avonmouth in southwest England. All five belong to Global Cruise Lines Ltd., which has its headquarters in Greece.

Coast guards say the ships will be detained until the labor breaches are resolved.

Cruise lines stopped sailing in mid-March after several large coronavirus outbreaks at sea, and thousands of seafarers remain stranded.

The All India Seafarers Union wrote to the Indian government last week seeking help for Indian crew aboard the Astoria it said were “stuck in foreign waters.”