A U.S. magistrate yesterday ordered Ibrahim Awadllah, 46, the owner of the Watergate Limousine Service, held on a $50,000 bond after his arrest Thursday on a charge that he allegedly caused a former bank official to help him illegally obtain $225,000 in bank funds.

Awadllah, who consistently has denied any wrongdoing, has been a key figure in a government investigation into more than $3.2 million in cashier's checks approved by Raymond C. Mowchan, who was the manager of the American Security Bank's Woodley Park branch. Mowchan has pleaded guilty to two counts of misapplication of bank funds and is scheduled to be sentenced Oct. 22. A grand jury is continuing to investigate the matter.

Assistant U.S. Attorney Charles H. Roistacher alleged in court papers filed prior to Awadllah's arrest that more than 190 cashier's checks totaling more than $3 million were drawn on the American Security Bank from January 1980 to February 1982 and that most were payable to Awadllah or his creditors.

Roistacher has said in court that Awadllah allegedly gave Mowchan worthless personal checks in exchange for the cashier's checks, and that Mowchan transferred funds from other customers' accounts to cover the shortfall. Awadllah, who was expected to post bond last night, has insisted that the money he received from Mowchan represented loans from another party and that these loans were repaid in full.

Roistacher said yesterday that a government witness alleged Awadllah had threatened her and harassed her in telephone calls. Awadllah denied this.

Magistrate Lawrence Margolis set bond for Awadllah at $50,000 on condition that Adwadllah avoid contact with any witnesses in the case.