This follows an incident earlier in the week in which a resident in the 7800 block of Durham in the Heatherwood subdivision reported hearing an explosion.
The next morning, an explosive device was recovered.
An earlier incident occurred on July 1 when someone threw one of the homemade devices from a pickup truck and a bystander kicked it, causing it to explode.
Boulder County Sheriff Commander Rick Brough said all the devices are similar.
They are 12-to-16 ounce capped plastic bottles that contain a liquid chemical and aluminum foil.
In the latest incidents, Brough said deputies went to the Somerset subdivision swimming pool about 3 p.m. Wednesday on a report of a suspicious container.
Brough said the deputies found the remnants of four explosive devices – plastic bottles that had erupted – in the area around the pool, tennis courts and in an adjacent field.
He said one of the devices was thrown into the pool house where it exploded, causing about $1,000 in damage.
About 12:50 a.m. today, a deputy patrolling the subdivision located three more explosive devices in the same area.
Brough said that because of the multiple incidents involving the exploding bottles, the public needs to be cautious. The chemical reaction in the bottles produces hydrogen gas which is flammable, said Brough.
The most recent incident occurred late Monday night when a resident in the 7800 block of Durham Way in the Heatherwood subdivision reported hearing an explosion.
Tuesday morning, a ruptured plastic bottle with its lid intact was found near the location of the explosion reported at 11:30 p.m. Tuesday.
The sheriff’s office said that the bottle had been ruptured from some type of an explosion.
An additional search of the subdivision by sheriff’s deputies failed to find any additional devices.
Sheriff’s Commander Rick Brough said that at 8 p.m. on July 1, a plastic bottle was thrown from a black Chevrolet pickup at the intersection of Pawnee and Longview Drive in the Morton Heights subdivision in Niwot.
When a witness kicked the bottle, it exploded, said Brough. Neither the person kicking the bottle nor a second person standing nearby were injured.
Brough said the bottle contained chemicals that when combined created an explosion.
Brough said the Boulder Sheriff’s Office is warning the public of the two incidents because of the dangers involved.
In both Monday night’s incident, and the one in July, the devices were 12-16 ounce capped plastic bottles that contained a liquid chemical and aluminum foil.
Citizens are being cautioned against picking up suspicious containers that are found in their mailboxes, the street or on their lawns.