The Kamayani Express was on its way to Mumbai when it derailed late Tuesday night near the town of Harda in Madhya Pradesh state, while the Janata Express was traveling in the opposite direction when it slid off the tracks soon after.
The trains were crossing a small bridge near the Machak River, about 950 kilometers (590 miles) south of New Delhi. Another train had passed the same culvert 10 minutes before the first derailment without any problem, but then a flash flood caused part of the track to sink into the rain-soaked ground, said A.K. Mittal, a senior railway officer.
Six coaches from the Kamayani Express and the engine and four coaches from the Janata Express derailed just before midnight. Although rescue workers soon reached the site, they were slowed by darkness.
At least two coaches were partially submerged in the mud, said railway official Anil Saksena. While most people had been pulled to safety, rescue workers were still searching for passengers likely trapped.
"Most of the coaches had passed but the last few carriages were derailed," Saksena said.
Television footage showed some train cars fallen on one side and others leaning in the mud. Tracks were broken, uprooted and scattered, and one train wheel had detached.
At least 24 bodies have been recovered so far and one person was seriously injured, said Bijendra Kumar, a railway official in Bhopal, the main city in Madhya Pradesh.
By late evening the bodies of those killed, covered in white shrouds, had begun to arrive at the Harda railway station where grieving relatives waited.
Junior Home Minister Kiren Rijiju said more than 300 people have been rescued.
Kumar said railway workers would soon start repairing the tracks so traffic can resume. Dozens of trains have been stopped while others have been diverted.
Prime Minister Narendra Modi tweeted: "The two train accidents in Madhya Pradesh are deeply distressing. Deeply pained over the loss of lives."
Heavy monsoon rains have killed more than 100 people in western and eastern India in the past week, flooding rivers and fields, and forcing tens of thousands to take shelter in state-run relief camps.
The rain eased Wednesday following two days of heavy downpour.
India has one of the world's largest railway networks and carries more than 23 million passengers each day. However, many parts of the vast network are poorly maintained and accidents are common. Earlier this year, Modi's government announced plans for a $137 billion overhaul of the railway's crumbling infrastructure over the next five years.
While many trains are called express, they rarely travel faster than 50 kilometers (30 miles) an hour. The extensive train network remains the main means of transportation for people and goods.
(AP)