WASHINGTON (AP) _ The next phase of the House bank probe will scrutinize a small number of past and present lawmakers for check kiting, writing large overdrafts or mixing campaign and personal funds, a source close to the investigation says.

Justice Department special counsel Malcolm R. Wilkey reported ''possible criminal conduct'' Wednesday by a few account holders at the now-closed House bank.

He reported his preliminary findings to Attorney General William P. Barr, who immediately created a new prosecution unit for the case. The unit is made up of career attorneys who assisted Wilkey.

The source, speaking only on condition of anonymity, said those still under scrutiny have engaged in ''classical'' check kiting, repeatedly wrote large overdrafts and deposited campaign money in their personal accounts.

''The House bank was a convenient place to launder things if you wanted to do it,'' said the source. ''Members had a comforting feeling that no one was looking at the bank except another arm of Congress, the General Accounting Office, and the GAO had a friendly attitude.''

Prosecutors now must determine whether the targets of the probe - at this time mostly former House members - had criminal intent.

An Associated Press survey shows 17 House members have not said they have received letters clearing them, including three who were re-elected to the next Congress.

Wilkey said the names referred to the new investigative unit were ''almost entirely'' former House members. But he made clear that some current members are still in limbo, neither cleared nor referred. These are members whose accounts were complicated or have not yet furnished necessary information.

Some of the account holders were doing check-kiting ''in the classical mode,'' said the source with knowledge of the probe. ''Most of those left (under investigation) had a large number of separate acts.''

Kiting involves writing a check knowing there are insufficient funds in the account. The idea is to replenish that account with a second check drawn on another account with insufficient funds.

Wilkey's report said the House bank ''offered a golden opportunity'' for the practice, with ''two great advantages.''

The bank permitted an additional period of delay before the member had to make good the original bad check. More importantly, Wilkey said, was ''the comforting knowledge that his original bad check would never be sent back through channels without him knowing about it and having a chance to recover it.''

He referred to the bank's system of first covering bad checks without any penalty, and then notifying problem account holders by telephone of their insufficient funds.

Check kiting usually is prosecuted under one of the federal fraud statutes.

Others still under investigation simply wrote overdrafts for large sums on several occasions, giving them use of the interest-free loans. Since funds in the accounts were considered public dollars, this could be conversion of government funds to personal use.

Some of those still under investigation deposited money from their campaigns in their House accounts, the source said.

This only would be legal to repay a loan that someone made to his or her campaign. The transaction must be reported to the Federal Election Commission.

Some lawmakers also may have violated laws on reporting campaign transactions and income. Disclosures are required by the FEC and the House.