Six Maryland Rail Commuter trains to the District were delayed early yesterday after a leak was discovered in a propane car in a CSX Corp. railroad yard near Brunswick, Md.

CSX workers spotted a spray coming out of the top of a tank car holding about 30,000 gallons of liquid propane about 3:20 a.m., said CSX spokesman Norman E. Going. Rail yard workers determined that the source of the spray was an open relief valve, which normally opens and shuts to allow the escape of minute amounts of gas to relieve pressure in the tank.

CSX moved the car for repair work to a spot in the yard that blocked some of MARC's stored equipment, delaying the first commuter train for an hour, said Maryland State Railroad Administrator Richard Keene. The second MARC train ran 40 minutes late. Four others were delayed from two to seven minutes, he said.

CSX repaired the tank car by 6:25 a.m., Going said. One CSX crew member felt ill and was taken to a nearby hospital, where he was treated and released, Going said. CSX does not know how much propane escaped but believes it was "mostly fumes," a spokesman said.

In unrelated developments:Three tank cars carrying chlorine derailed yesterday in Conrail's Edge Moor, Del., yard near Wilmington.

The cars, part of a 36-car freight train pulled by one locomotive, turned onto their sides about 9 a.m., but did not leak or cause any injuries, said Conrail spokeswoman Pat Linskey. A wildcat strike by Amtrak employes in New Haven, Conn., caused minimal delays to trains serving the Washington area yesterday, said Amtrak spokesman R. Clifford Black.

Members of the International Association of Machinists and Aerospace Workers organized the strike to protest the layoffs of 32 employes at the New Haven rail yard shops. A federal judge ordered the employes back to work last night.

The strike caused delays of up to 20 minutes to trains traveling south from Boston through New Haven, Black said. The action forced the cancellation of one Metroliner from New Haven to New York City, but the extra equipment was used to provide Metroliner service from New York to Washington, Black said.