Police in northern Mexico have arrested eight people for allegedly killing two 10-year-old boys and a 55-year-old woman in ritual sacrifices.

Prosecutors in the state of Sonoru say the alleged suspects belong to the cult of La Santa Muerte, or Saint Death.

Jose Larrinaga, a spokesman for Sonora state prosecutors, said the victims' blood was poured around an altar to the saint, which is depicted as a skeleton holding a scythe and clothed in flowing robes.

The cult, which reveres death, has been growing rapidly in Mexico among drug traffickers and criminals in recent years, but there have been no confirmed cases of human sacrifices in the country.

Larrinaga said the first of the three victims was apparently killed in 2009, the second in 2010 and the latest earlier this month.

Investigations indicate their throats were slit, they had cuts on their wrists and their blood was poured around an altar to the saint.

"They sliced open the victims' veins and, while they were still alive, they waited for them to bleed to death and collected the blood in a container," added Larrinaga.

Authorities began investigations after 10-year-old Jesus Octavio Martinez Yanez was reported missing on March 6 by his stepfather.

Investigations led authorities to an apparent altar site in the Sonora city of Nacozari, about 110km south of Douglas, Arizona.

Larrinaga said the arrests were made after tests by forensic experts on Thursday found blood traces spread over 30 square meters there.

Larrinaga said the murders took place at a ritual during the night, lit by candles.

Those arrested included Silvia Meraz and her son Ramon Palacios, who allegedly killed the victims.

Speaking to reporters, she said: "We all agreed to do it. Supposedly she [one of the victims] was a witch or something."

She did not respond to questions about the boys' killings.

The other suspects, many of them relatives, included people ranging from a 15-year-old girl to a 44-year-old woman.

Source: Agencies