(CNN) -- Russia's child rights ombudsman slammed Texas prosecutors for deciding not to charge the adoptive parents of a Russian boy who died suddenly, Russia's RIA Novosti news agency reported Tuesday.
On Monday, the Ector County district attorney said a grand jury declined to indict Laura and Alan Shatto, the adoptive parents of 3-year-old Max Shatto.
A Texas coroner had declared Max's death in January accidental, but Moscow demanded a complete report from U.S. officials.
Russian Children's Rights Commissioner Pavel Astakhov claimed the district attorney's office has not done enough in investigating the case of Max, also known as Maxim Kuzmin.
"The Texas prosecutors' position in the case of Maxim Kuzmin is upsetting, because they refused to scrutinize the circumstances of his death," Astakhov tweeted, according to RIA Novosti.
But District Attorney Bobby Bland said the grand jury found no evidence to charge the Shattos.
"This death was the result of a tragic accident occurring most likely on playground equipment," Bland's office said, according to CNN affiliate KOSA.
"When a child dies so young and tragically, it is natural to want to hold someone accountable. However, in this case, there is no evidence to support holding anybody criminally responsible."
Investigating the death
This month, Bland told CNN that said four pathologists and the Ector County medical examiner attributed the death to a laceration of a small bowel mesentery artery because of blunt trauma to the abdominal area.
The bruising was consistent with a "self-inflicted" injury, Bland said.
A statement from the Ector County Sheriff's Office said the boy "had previously been seen for a behavioral disorder that manifested itself in self-injury and these bruises were consistent with that diagnosis."
Astakhov had accused the adoptive mother of killing the boy and giving him "psychotropic substances," RIA Novosti reported.
But toxicology reports were negative, and there were no substances found that could have contributed to the child's death.
International strain on adoptions
The death drew international attention after Astakhov said that the boy was "killed" or "murdered."
In February, Astakhov said he tweeted those words based on the initial reports he received about the death but acknowledged he may have spoken too soon.
Still, he said he wanted his country to ban all international adoptions of Russian children.
Moscow passed a law in December banning adoptions of Russian children by Americans.
That pending law was set ostensibly because of documented cases of abuse by adoptive parents. But some say the Russian move was retaliation for a U.S. law that places restrictions on Russian human rights abusers.
Max's death aggravated U.S. State Department efforts to push through more than 500 adoption cases in which American families have already begun the process of adopting a Russian child.
Americans adopted nearly 1,000 Russian children last year, according to State Department figures.
Though the number has been dropping in recent years, Russia remains the third most popular foreign country -- after China and Ethiopia -- for U.S. foreign adoptions.