A $4 million (€3 million) painting by pop art legend Roy Lichtenstein was returned on Tuesday to its rightful owner, 42 years after it went missing, the FBI said.

Celebrated art dealer Leo Castelli acquired Electric Cord in the 1960s and displayed it in his New York gallery, but it disappeared after he sent it out to art restorer Daniel Goldreyer for cleaning in 1970.

It turned up again in July this year at a New York storage facility, which received it after it had been consigned to an art gallery in Colombia’s capital Bogota for sale.

Goldreyer’s widow told investigators she had been asked by a friend of her late husband to sell it on his behalf, the FBI said in a statement.

She formally relinquished all claims to the painting, clearing the way for its return to Castelli’s widow, Barbara Bertozzi Castelli. She intends to hang it in her apartment, local media reported.

“The return of Roy Lichtenstein’s Electric Cord to its rightful owner really serves the interests of justice,” said Mary Galligan of the New York office of the Federal Bureau of Investigation.