ADEJE, Spain — Among the hundreds of guests who remained stranded in a hotel in the Canary Islands on Thursday, after four guests were found to have the coronavirus early this week, an overriding question loomed:

“What’s going on?” Romane Guilloux, 20, a guest from France, asked about the lockdown imposed on patrons of the hotel, the H10 Costa Adeje Palace, a four-star resort in the south of Tenerife, the largest of the islands.

Several European countries reported their first coronavirus cases on Thursday, and Britain confirmed a case that was linked to Tenerife. Some countries were taking aggressive steps to halt contagion of the virus, from shutting schools to closing mosques.

But at the Costa Adeje Palace, where officials said more than 700 people from 25 countries were staying, confusion reigned. Some guests appeared to be deeply frustrated, uncertain about how long they will have to remain in isolation and upset over what some thought were loose hygiene practices that might increase the chances of the virus spreading.

Guests have been allowed to mingle around the resort’s pools. They have dined in the hotel’s restaurants and wandered in the common areas. The hotel staff has gone home when not working. Such measures have alarmed medical experts.