SEABROOK, N.H. — Authorities blamed human error Thursday for some sirens that were inadvertently activated at a New Hampshire nuclear power station last month.

The state Homeland Security and Emergency Management agency and plant owner NextEra Energy Resources put out statements more than 30 minutes after beachgoers in nearby Hampton and Rye said they heard announcements about the beaches being closed on July 12 because of a problem at the plant. Ten of the 121 sirens were activated. The announcements sent some beachgoers scrambling but officials said that there was no emergency nor danger to the public.

The plant is about 40 miles north of Boston and 10 miles south of Portsmouth. It has operated since 1990.

Lindsay Robertson, a spokesperson for the nuclear power station, said the findings of the investigation have led to several policy changes including revising the process for silent testing of the emergency sirens, enhanced management oversight during a a system test and the retraining of staff who test the emergency siren system.

“The station conducted a thorough investigation and concluded that human error resulted in the inadvertent activation of some sirens on the New Hampshire Seacoast,” Robertson said. “Inspections concluded that the emergency siren system had no equipment issues.”