Dyfed Powys Police were called to New Road, Pontyberem, Carmarthenshire, Mid Wales, at 8.30am today.
Six-day-old Eliza-Mae was airlifted to the University of Wales Hospital in Cardiff, where she was pronounced dead.
“A police investigation is under way following the sudden death of an infant at a property in Pontyberem,” a force spokeswoman said.
“As part of inquiries, the family dog has been seized. Inquiries are ongoing.”
The dog seized from the property was an Alaskan Malamute, the spokeswoman confirmed.
Alaskan Malamutes were originally bred as sled dogs for work in the Arctic, but are now popular as family pets.
The Alaskan Malamute Club of the United Kingdom describes the breed as an “affectionate, friendly, loyal, devoted companion” on its website.
An ideal Alaskan Malamute is “heavily boned, powerfully built”, it says.
Alan Lewis, chairman of Pontyberem Community Council, said: “We are only a village of 2,500 to 3,000.
“It is a huge shock for the particular community. Our thoughts go to the family involved, obviously.
“From what I understand, the police are still continuing their investigations and the area is cordoned off.”
Mr Lewis described Pontyberem as a “an ex-mining community village”.
The cause of Eliza-Mae’s death has not yet been released and police say investigations are still at an “early stage”.