The Ministry of Risk Management said four trucks, one car and two bikes fell about 50 km (31 miles) north of Guayaquil Port.
The AFP reported at least five people injured.
At one end of the bridge, a truck trailer carrying a large amount of corn lay on its side, wobbling the guardrail.
The bridge connects to Guayas, where Guayaquil is located, and other states to the north.
Guayas Governor Marcela Aginaga said he has not received any reports of it being defective.
“From what we can guess at this point, the bridge has become overloaded,” she added to Social Network X.
The collapse of the bridge comes in the middle of the rainy season in the Andes.
At least 20 people have been killed in floods and landslides that damaged 45 bridges, the report added.
MA/PR