An exploding water bottle bomb Friday afternoon brought Anchorage police to the 800 block of Fourth Avenue, between Muldoon Road and Duben Avenue, police said.
Investigators don't know where the plastic water bottle bomb came from but it's the sort that police have encountered before.
"Generally it's teens that learn how to make them using an Internet video and then dump them around neighborhoods, playgrounds, etc.," police spokeswoman Jennifer Castro said in an email.
A resident called police around 4 p.m. about an explosion in the yard. Police say they found pieces of an exploded water bottle, bits of foil and evidence of a liquid chemical.
The resident heard more than one explosion, so there were likely at least two water bottle bombs, Castro said.
More may have been left in the area. Police say if you find one, don't pick it up; instead, call police.
"Acid or liquid chemical bombs can explode with or without contact, and sometimes within minutes or hours of being produced," police said in a statement.