Nigerian authorities have launched an investigation following the recent death in a Lagos hospital of the baby of bestselling Nigerian writer Chimamanda Ngozi Adichie, who accused the facility of "gross negligence".

Nkanu Nnamdi, 21 months, one of the twins the author had with her doctor husband, Ivara Esege, died on January 7 "after a brief illness," according to a private communication from Ms. Adichie that was subsequently leaked to the public.

Having fallen ill, the child was taken to the hospital for an MRI and other tests in preparation for repatriation to the United States, where Ms. Adichie lives.

The family was in Nigeria for the end-of-year holidays.

The author and her husband have sent a formal notice to Euracare Multispecialist Hospital, a renowned private facility in Lagos, which they accuse of "serious medical negligence," Omawumi Ogbe, a family spokesperson, told AFP on Wednesday.

The latter points to "devastating clinical failures" that led to the child's death, adding that she "eagerly awaits the truth and the acknowledgment of responsibility."

The Lagos State government has ordered an investigation into the circumstances surrounding this death.

Euracare did not immediately respond to AFP's request for comment on Wednesday.

Chimamanda Ngozi Adichie's sister-in-law, herself a doctor, told Nigerian television that the boy had been given an excessive dose of anesthetic in order to have an MRI scan and that the anesthesiologist had not followed the proper medical protocol.

The level of healthcare in Nigeria is generally considered inadequate, and those who can afford it, including senior political leaders, often seek treatment abroad.

Around 850,000 newborns and children under five die each year in Nigeria from preventable causes, the health minister acknowledged last month.

According to the World Bank, Nigeria has the second highest infant mortality rate for children under five in the world, just behind its neighbour Niger.

Nigeria, Africa's fourth-largest economy, is a major producer of gas and oil, has a thriving business culture and boasts global pop stars, but lacks basic infrastructure, particularly in water, electricity and quality healthcare.

In 2024, the government revealed that between 15,000 and 16,000 doctors had left Nigeria in the past five years.

Africa's most populous country has only 300,000 health professionals, including 55,000 doctors, for a population of 220 million, and most of the healthcare workers are located in major cities.

In Lagos, a megacity of over 20 million inhabitants, there are only about a hundred ambulances.