BALETE, Philippines — Taal Volcano’s eruptions have eased in the past 24 hours, scientists said on Wednesday, but they warned that the picturesque mountain was still threatening hundreds of thousands of people just 40 miles south of Manila.

Renato Solidum, Jr., who leads the Philippine Institute of Volcanology and Seismology, said that Taal’s calm could be deceptive.

“What we’re saying is that it was generally weaker compared with yesterday,” Mr. Solidum said, adding that it was “hard to tell” if the mountain was also easing its rumbling.

Taal, the Philippines’ second-most-active volcano, surprised even volcanologists when it suddenly erupted on Sunday. Within hours, the volcano on an island in the middle of a lake shot a plume of ash a mile high and triggered multiple earthquakes.