Cleaners working on London's subway network are staging a 48-hour strike in a dispute over pay during the Olympics.

Members of the Rail Maritime and Transport union who work as cleaners for two private contractors walked out at 5:30 a.m. (0430 GMT, 12:30 a.m. EDT) Thursday.

The transport union has said the strike means no cleaners will be working in the part of the subway, or Tube, near the Olympic Park.

Picket lines will be set up outside several Tube stations, including Stratford, the main stop for the Olympic Park.

General secretary Bob Crow has said the strike is to protest the "minimum pay rates" that transport cleaners are paid to do "some of the dirtiest jobs."