(CNN) -- A possible constitutional crisis loomed in Malawi following the reported death of President Bingu wa Mutharika, once hailed as a positive steward for the southern African country.
Mutharika, 78, died of a heart attack on Thursday and his body was flown to South Africa, according to government sources.
However, there was no formal government statement announcing his death, and the chaotic politics of the impoverished nation raised questions about what happens next.
Under the constitution, Vice President Joyce Banda would succeed Mutharika.
However, Banda was expelled from the ruling Democratic People's Party in 2010 in a dispute with Mutharika over the president's efforts to position his brother rather than the vice president as his eventual successor.
Banda formed her own party, but remained vice president.
A government spokeswoman declined to discuss reports of the president's death but declared that the vice president cannot take over the presidency.
"The conduct of the honorable Joyce Banda in forming her own opposition party precludes her from being eligible to succeed the presidency," said Patricia Kaliati, who serves as information and civic education minister.
In a news conference earlier Friday, Banda told reporters she was kept "in the dark" regarding the president's condition.
However, the Malawi defence forces, which provides security for the sitting president, shifted security members to Banda's residence amid news of the death.
While declining to comment on the president's condition, Kaliati appealed to Malawi residents to remain calm and only listen to information coming from official government sources.
The United States and Britain have urged Malawi to observe the succession process in the constitution.
"We are concerned about the delay in the transfer of power. We trust that the vice president who is next in line will be sworn in shortly," said Johnnie Carson, the U.S. assistant secretary of state for African affairs.
During her news conference, Banda, along with former President Bakili Muluzi, called on Malawians to adhere to the constitution regarding the issue of succession.
Mutharika, a former World Bank economist who studied in the United States and other countries, was elected president in 2004 after campaigning as an "economic engineer." He won re-election five years later for a term scheduled to end in 2014.
His initial years in office were considered a success as he focused on battling corruption and working to improve the economy.
He implemented a subsidy program for agricultural products that was credited with boosting the economy of the largely agrarian nation. Malawians welcomed his focus on reducing reliance on food aid and attaining self-sufficiency.
However, his popularity plunged in recent years as the economy faltered and the nation faced chronic fuel shortages and frequent power blackouts.
Anti-government groups accused Mutharika of dragging Malawi back into a dictatorship, citing the passage of bills they say infringe on citizen rights.
Protesters took to the streets last year demanding immediate government action to address the economic plight. Security forces cracked down, leading to more than a dozen deaths and sparking international condemnation.
Critics also accused Mutharika of jeopardizing international relations and risking foreign aid that benefits the nation's poor.
Last year, Mutharika expelled a British envoy who was quoted criticizing him in a leaked diplomatic cable, straining relations with one of Malawi's largest foreign donors. In return, Britain asked Malawi's top envoy to leave the country and rescinded her invitation to the royal wedding.
At the time, London said it was halting "all general budget support" to the nation.
Last month, the United States announced it was suspending $350 million allocated to Malawi because of concerns about its democratic governance.
CNN's Nkepile Mabuse and journalist Gregory Gondwe contributed to this report.