A woman died shortly after delivering a baby, and four other new mothers fell critically ill on Friday morning at Midnapore Medical College and Hospital after allegedly being administered a banned intravenous injection that was also past its expiry date.

The deceased, 30-year-old Mamoni Ruidas of Garbeta in West Midnapore, succumbed after giving birth to a baby boy, while the four other women remain on ventilation in the intensive care unit, battling for their lives.

Sources, including several doctors who spoke on condition of anonymity, alleged that the intravenous injection, "lactated ringers" or "ringer lactate", commonly known as sodium lactate solution, was toxic as it had expired.

The injections were reportedly supplied by a company based in North Dinajpur's Chopra that had been blacklisted last year by the Karnataka government for substandard products and the Bengal government had asked medical facilities not to use the drug.

Lactated ringers, a crystalloid fluid used to replenish water and electrolytes, are commonly administered to puerperal mothers to treat conditions like low blood pressure and sepsis.

The incident caused widespread outrage, with patients' relatives questioning the credibility of medicines supplied to government-run healthcare facilities. Anticipating unrest, the district administration deployed additional police forces on the hospital premises.

Relatives and hospital sources reported several women developed complications on Wednesday night after undergoing Cesarean sections. By Friday morning, Mamoni Ruidas, who had delivered a baby boy, had died.

Mamoni's husband, Debasish Ruidas, alleged negligence.

"Shortly after saline was administered, Mamoni's urination stopped and she died on Friday," an inconsolable Debasish said.

The incident has prompted the state health department to launch an investigation. Initial inquiry revealed the saline injections had expired.

State health secretary Narayan Swarup Nigam confirmed a probe had been ordered and an immediate report sought from hospital authorities. A specially formed 11-member investigation team is expected to visit the hospital on Saturday.