'There isn't any serious indication from the submarine, ' Navy spokesman Enrique Balbi told the Todo Noticias channel.
Argentina Navy submarine ARA SAN JUAN disappeared in waters of Puerto Madryn, northern Patagonia, Argentina, contact with submarine manned with 40 crew lost since Nov 15.
The last radio contact with the San Juan submarine was on Wednesday, when it was 430km off the coast of the southern province of Chubut, in the area of San Jorge bay, a naval spokesman said on Friday.
At least 44 crew members were on board, state-run news agency Telam reported Friday.
He called to "be careful", because "we don't know what happened, I don't want to sensationalize this case".
The TR-1700 class diesel electric submarine had been returning from a routine mission to Ushuaia near the southernmost tip of South America, to its base at Mar del Plata, around 400 kilometers (240 miles) south of Buenos Aires.
Speaking of a "communication failure", the navy said the submarine is not considered lost, while Balbi denied a report that there may have been a fire onboard. "We have a loss of communications; we are not talking of an emergency", he said.
Balbi said the submarine had enough food for several days.
It was built in Germany in 1985 and arrived in Argentina a year later.
"The navy is conducting operations to resume communications with the ARA "San Juan" submarine", the navy said on Twitter.