The electrical shock delivered to the chest by a Taser can lead to cardiac arrest and sudden death, according to a new study, although it is unknown how frequently such deaths occur.

The study, which analyzed detailed records from the cases of eight people who went into cardiac arrest after receiving shocks from a Taser X26 fired at a distance, is likely to add to the debate about the safety of the weapons. Seven of the people in the study died; one survived.

Advocacy groups like Amnesty International have argued that Tasers, the most widely used of a class of weapons known as electrical control devices, are potentially lethal and that stricter rules should govern their use.

But proponents maintain that the devices — which are used by more than 16,700 law enforcement agencies in 107 countries, said Steve Tuttle, a spokesman for Taser — pose less risk to civilians than firearms and are safer for police officers than physically tackling a suspect. The results of studies of the devices’ safety in humans have been mixed.