Thieves tunneled into a downtown Los Angeles jewelry store, stealing millions in merchandise and cash, according to a report by NBC Los Angeles.

The owners of Love Jewels, a family-operated store, discovered the sophisticated break-in after the weekend and estimate losses could reach $20 million.

“They probably went in there every night, slowly dug until there was enough room,” said the owner’s son, speaking anonymously to NBC4. He suspects the thieves used the adjacent abandoned theater as their operational base, possibly spending weeks completing the tunnel.

The burglars disabled security cameras and alarms, gaining several hours to breach two safes.

“In the gold business, you reinvest everything, so all our money was in the safe,” the son explained, emphasizing the severe impact on their business.

Police have not confirmed the exact loss amount but are investigating.

Read more at NBC Los Angeles