The family of eight that was stabbed to death in the northern Mexico border city of Ciudad Juarez may have known their killers, according to Chihuahua officials.
No signs of forced entry into the house have been found and the knife used for the murder was allegedly from the kitchen, state prosecutor Enrique Villareal said at a news conference.
Other reports indicate that some of the adults were killed with a machete.
The victims, who included two 4-year-olds (Abril Romero and Valeria Lara Castañeda) and a 6-year-old (Daniel Romero Castañeda), were found with tape over their mouths and their hands tied. The oldest, named as María del Carmen Morales Infante, was aged 60.
In total two men, three women and three children were slaughtered. A three-month-old girl in the house was found alive.
Enrique Serrano, mayor of the city, said: "We deeply reject this act and hope to have results soon". He offered a reward of almost $25,000 for information leading to the arrest.
Authorities are focusing on potential robbery or family dispute motivesf for the macabre killing, and have rejected any links to organised crime.
One of the victims, Maximo Martin Romero Sánchez - nicknamed Max - aged 27, sold used cars at his home and may have had cash with him at the time of the killing.
Officials said they were questioning two people but did not give further indications.
The eight were found on Sunday morning after they did not attend a Jehovah's Witness meeting and congregation members became concerned.
Ciudad Juarez, across the border from El Paso in Texas, was considered the world's most violent city due to a bloody war among drug cartels.
However, the murder rate has declined since President Enrique Pena Nieto was elected last December. According to federal statistics, homicides increased in 2010 to a peak of 3,900 and have dropped to 1,134 in the first nine months of this year.
Around 10,000 people have been killed in the city since 2006.
In September, a gang of gunmen killed 10 people, including a six-year-old girl, in the area.