The Army said yesterday that there is only one investigation of C3 Inc., a Reston computer systems firm that does nearly all of its business with the Pentagon.

An official with the Army's Office of the Judge Advocate General confirmed that there is a single, ongoing criminal investigation of the company. Neither the Army nor attorneys for C3 would elaborate on details of the investigation.

The Washington Post reported Wednesday that there was a second investigation.

Army officials said the investigation of C3 is being conducted by another federal agency, but that it is the same investigation that led to the suspension of the company from bidding on future defense contracts.

The Army had suspended C3 on Oct. 15, charging that the company had made false statements and claims in connection with a contract administered by the Defense Supply Service. That suspension was lifted Wednesday after attorneys for C3 questioned facts used by the Army in taking its action.

"They made an excellent presentation that raised substantial issues of fact," an Army official said yesterday. The Army said it decided to lift the suspension rather than resort to fact finding that would have involved calling witnesses who also were involved in the ongoing investigation.