NEW: Police suspect man of lighting a fire on February 7
NEW: He is charged with arson causing death, possessing child pornography
Number of fires burning has dropped to 21 from about 35; at least 181 people killed
Australian PM announces memorial service and national day of mourning
Man charged with arson in Australia wildfires
KINGLAKE, Australia (CNN) -- Police have arrested a man in connection with one of the myriad wildfires that have laid waste to parts of southeastern Australia and killed at least 181 people.
1 of 2 more photos » Police say the man is suspected of lighting a fire on February 7. He was charged with arson causing death, intentionally or recklessly lighting a bush fire, and possessing child pornography, according to a statement by the Victoria state police.
The man, who was not named, is suspected of starting a blaze called the Churchill fire.
The development came as the blazes that have roared through the region for nearly a week were slowly coming under control.
The Country Fire Authority said the number of fires burning had dropped to 21 from about 35 on Thursday. Watch a survivor tell his story »
While "the threat will remain for weeks to come," a spokesman said no towns were under threat Friday morning and that good weather had allowed firefighters to build containment lines around the fires.
Meanwhile, more than 150 detectives were working on an arson investigation, authorities said.
Two men who were arrested for "suspicious behavior" on Thursday were released without charges.
"We are satisfied with their explanation and don't expect to talk to them again," Victoria state police inspector Peter Sheppard said.