Tens of thousands of people heading home from yesterday's concerts and fireworks on the Mall mobbed downtown subway stations in what Metro officials said was the worst crush of riders in recent years.

Although transit police took measures to control the flow of riders onto the station platforms, sweltering heat and the press of the crowds caused scores of people to faint at the Smithsonian and Metro Center stations. Red Cross officials said as many as 10 persons were taken by ambulance from the Smithsonian stop at 12th Street and Independence Avenue NW. Other victims of the crush resumed their trips after lying down in remote areas of the stations.

D.C. Fire Department officials said hundreds of others collapsed after the festivities in the Mall area, and at one point ambulances were reported running more than an hour behind on emergency calls.

"They're dropping like flies," a D.C. paramedic reported to fire officials as he requested more ambulances about 11 p.m.

This is the worst I've seen it in eight years," Metro's Randall H. Laughlin said surveying the crowd at Metro Center. "There are just too many people. It took 12 hours to get everybody down here and everybody wants to get back in two."

Trains were running every four to six minutes, but many of those reaching the Smithsonian, Metro Center and L'Enfant Plaza stations were already filled to near capacity, and passengers lining the platforms had to wait 20 to 30 minutes in the steamy hot stations before they could board.

A Metro police official estimated that 200,000 persons had entered the Smithsonian stop yesterday. He said that at the peak of last night's jam there, "You couldn't see the ground, you couldn't see anything but heads . . . all the way for as far as your eyes could see in every direction."