Federal magistrates ordered Thomas E. Spinks of Bowie and Kenneth William Shields of Laurel held without bail yesterday pending further hearings on charges that they participated in eight antiabortion bombings in the Washington area.

The two men were arrested Saturday along with a third Maryland man, Michael Donald Bray. Bray, 32, of Bowie, also is being held without bail.

A preliminary hearing date of Jan. 29 was set for Spinks, 37, at a bond hearing in a federal courtroom in Hyattsville attended by nearly a dozen news reporters and a man who identified himself as Spinks' brother.

Similar hearings to determine whether the other two men can continue to be held without bail are scheduled for today, in Bray's case, and for Thursday, in the case against Shields, 34. The charges carry penalties up to 25 years in jail and the men may be charged with more than one count.

Late last night agents of the federal Bureau of Alcohol, Tobacco and Firearms were searching a warehouse space at the Severna Office and Storage Park Mini Warehouse Group in Millersville, Md. They reported seizing several cylinders and other materials similar to those used in the bombings.

An ATF spokesman said the space had been rented in the name of Lou Burns, an alias the ATF has alleged that Spinks used to purchase chemicals.

At Spinks' hearing, federal investigators carried into the courtroom a device resembling a fire extinguisher wrapped with silver tape. Officials from the federal Bureau of Alcohol, Tobacco and Firearms reported finding in Spinks' home "ready-to-go" bombs as well as materials used in the manufacture of bombs.

Magistrate George E. Burgess agreed to deny bail after Spinks' court-appointed lawyer, Richard B. Bardos, did not object to the U.S. attorney's arguments. The magistrate scheduled a preliminary hearing to be held in Baltimore Jan. 29 to determine if federal prosecutors have probable cause to try Spinks.

Magistrate W. Harris Grimsley in Alexandria agreed to continue until Thursday a bond hearing for Shields, whose Alexandria attorney, J. Frederick Sinclair, argued that he needed more time to study his client's case.