Guatemalan President Jimmy Morales said the search and rescue operation will continue for as long as it takes.
More than 1.7 million people have been affected by the disaster.
Volcanologists said the formation of a lava lake is obvious proof of the rise of magma to the surface.
Mud and other materials from the explosion fell on the Penjamo River and changed the water color.
An explosion on Saturday night hurled incandescent rocks and gases that damaged a Poás National Park’s office and also solar panels, a tower and a webcam from OVSICORI.
Vulcanologists conducted an inspection of Poás and found rocks of various diameters ranging from 40 centimeters to 2 meters (1.3-6.5 ft) that had been hurled as far as one kilometer through the air.
UPDATE: April 14. 10:34 a.m. : Vulcanologists from OVSICORI and the National Seismological Network reported two strong eruptions at 7:39 a.m. and 7:57 a.m. on Friday.
Vulcanologists say the increase in the emanation of gases, vapor and water from the Poás crater is caused by a volume of fresh magma from deeper levels that is pushing up toward the surface.
A National Seismological Network's report noted that low-intensity volcanic tremors are following ash explosions at Turrialba Volcano.
Authorities warned that National Police or Tourism Police officers will charge those responsible for tours into restricted areas with disobedience of authority.