IRVINE, Calif. (AP) – Trace amounts of the deadly poison ricin have been found in at least one jar of baby food that had been tampered with, the FBI said Wednesday.

The FBI and prosecutors are investigating two suspected cases of food tampering. No injuries or arrests have been reported, FBI spokeswoman Laura Eimiller said.

Authorities have not disclosed the amount of ricin discovered, the number of baby food jars that contained the poison or a possible motive.

On June 16, a man told Irvine police that as he was about to feed his son, he found a note inside a jar of baby food warning that it had been contaminated. A similar case was reported by an Irvine couple on May 31 involving the same baby food, Gerber Banana Yogurt, police said. A note was also found inside that jar.

Investigators were testing Gerber Banana Yogurt removed from the store where both jars were purchased. They did not specify whether the ricin was found in both jars.

Authorities did not disclose the contents of the notes but said they referred to an Irvine police officer.

The Gerber Products Co., based in Parsippany, N.J., is working with investigators. Authorities told the company the contamination “absolutely” occurred after the food was manufactured, said Gerber spokeswoman Terry Boylan.

Gerber baby food jars are vacuum sealed and should pop when opened. If they don’t, it could indicate they have been tampered with, Boylan said.

Ricin is made from castor beans and can be fatal if swallowed, inhaled or injected. A dose about the size of the head of a pin could be enough to kill an adult, according to the Centers for Disease Control and Prevention.