NEW YORK, Oct 28 (Reuters) - JPMorgan Chase ( JPM ), the

largest U.S. bank, has begun suing customers for check fraud,

saying they improperly withdrew funds by taking illegal

advantage of a temporary technical glitch that went viral on

TikTok.

The glitch in late August let customers deposit big checks

in ATMs and withdraw funds immediately before the checks could

clear, even if the checks later bounced.

Chase filed four lawsuits on Monday in federal courts in Los

Angeles, Houston and Miami, accusing two individuals and two

businesses of illegally retaining more than $661,000 after the

checks they deposited were deemed counterfeit or forged.

In the largest case, Chase said a Houston man still owes

$290,939.47 after withdrawing over two days most of a $335,000

check that a masked man deposited in his account on Aug. 29.

Chase said the check was rejected on Sept. 4.

The defendants did not answer, did not accept, or could not

immediately be reached with messages seeking comment on Monday.

All four lawsuits accuse the defendants of violating their

deposit agreements, and seek the return of improperly withdrawn

funds plus other costs.

JPMorgan ( JPM ), based in New York, said it is pursuing the cases

and cooperating with law enforcement to ensure that people are

held accountable.

Last month, the Wall Street Journal said the bank was

investigating thousands of possible check fraud incidents.

"Fraud is a crime that impacts everyone and undermines trust

in the banking system," JPMorgan ( JPM ) spokesman Drew Pusateri said in

a statement.

Check fraud is a federal crime. Many banks including Chase

let customers access some of the value of their checks until the

checks clear.