With a growing number of consumers quarantined at home, some old pastimes are getting a fresh look. Jigsaw puzzles, for both adults and children, are one activity of choice that has marketers scrambling to meet the unexpected demand.

“There has been a resurgence in jigsaw puzzles,” says Chris Byrne, a toy industry expert known as “The Toy Guy.” He notes that improvements in manufacturing, such as laser cutting, have made it both easier and cheaper to produce puzzles, making them one of the most profitable items in the toy aisle for brands and retailers.

The uptick began in early March, as many schools started announcing indefinite closures as a result of the growing threat of coronavirus. The majority of toy sales increases came from the games and puzzles category for the week ending March 14, according to research firm NPD Group Inc. “Consumers turned to toys that offer social interaction in the home at a time of social distancing,” says Juli Lennett, NPD Group’s toy industry analyst.

Like adult coloring books, puzzles had already been growing in popularity as a new and relaxing activity for stressed out grown-ups. In recent months, many toy makers have turned to adults as way of growing their revenue streams. One top puzzle brand, Ravensburger, recently announced plans for a jigsaw puzzle competition in North America later this year—though it’s unclear if the May event, based in Minneapolis, will continue as planned. A Ravensburger representative did not immediately return a request for comment.

As families adjust to their new lives, they’ve perhaps already plowed through their puzzle closets and are shopping for more. Some consumers report lengthy wait times for Amazon adult puzzle deliveries; indeed, the ecommerce giant recently told vendors it won’t accept new shipments of nonessentials until April 5. Many Ravensburger puzzle series of both 100-piece and 1,000-piece levels are currently sold out at Target.

Puzzle Warehouse, an online retailer, posted a note on its website that advises customers to “expect delays.” It is now taking one to two weeks instead of one day to ship orders, the company said, noting “the surge in online shopping from the ongoing outbreak is straining our shipping department.”