SAN MATEO -- A cache of old, volatile chemicals was blown up in a "very loud" but harmless explosion at a Parrott Drive home shortly after 9 p.m. Wednesday, police said.
A resident discovered the chemicals, which had been stored some time ago, and realized the hazard they presented and contacted the fire department around 4:30 p.m., according to San Mateo police Sgt. David Norris.
Fire officials "determined that the materials were highly volatile and not stable to move without precautions in place against potential explosion," according to a news release.
Norris did not have specific information about the type of chemicals involved, but said "they were clearly the type that may become more volatile when left unmaintained for an extended period of time."
The 400 block of Parrott Drive was evacuated, as well as a few residences on adjacent streets, Norris said. All households in a five-block radius were alerted to the situation via a reverse-911 auto-dialer and advised to shelter in place while the San Mateo Sheriff's Office Bomb Squad was summoned.
All the hazardous materials were eliminated in the explosion, and no one was injured, police said.
The police department offered safety tips for residents when dealing with unknown material, such as a suspicious object, odor, spilled or leaking liquid or powder.
"It's best to treat it as a hazardous substance until proven otherwise," police stated. "Do not disturb it, touch it or sniff it. Do not smoke or strike a light near it, and extinguish any open flames nearby. Turn off electrical equipment near it (especially fans). Secure or block off the area around it. Keep others away until public safety authorities arrive."
Authorities should be immediately notified by calling 911 or San Mateo police dispatch at 650-522-7700.
Contact Eric Kurhi at 408-920-5852. Follow him at Twitter.com/erickurhi.