A woman passed through security screening at New York's LaGuardia Airport (search) with a stun gun and knife in her purse -- but later discovered the mistake herself and alerted authorities.

The woman realized she was carrying the items Saturday after a short layover in Detroit and on her way to Denver.

"She immediately went, 'Oh, my God, I'm not supposed to have these here,' and called the flight attendant over," said Spirit Airlines (search) spokeswoman Laura Bennett.

The pilot alerted Denver International Airport (search); police met the plane at the gate and took the woman into custody for questioning. She was released without charges.

"She did the right thing by giving up the items voluntarily, and she was never malicious," Bennett said. "We never considered her a threat."

Transportation Security Administration officials had no comment on the security slip. TSA official Darrin Kayser said the agency would investigate.

"It was an honest but odd mistake," Bennett said. "But it's true that people often don't think about what's in their luggage."