(Reuters) - The White House admonished Russia on Wednesday after it vetoed a United Nations plan to continue an ongoing investigation that recently found Syria killed dozens of people with chemical weapons and implored the international body to renew the probe.   Russia cast a veto at the United Nations Security Council eight days ago, preventing the renewal of a mandate for a mission by the United Nations and the Organization for the Prohibition of Chemical Weapons (OPCW) - known as the Joint Investigative Mechanism (JIM) - that investigates the use of chemical weapons in Syria.  Russia s attempts to undermine and eliminate the JIM show a callous disregard for the suffering and loss of life caused by the use of chemical weapons and an utter lack of respect for international norms,  the White House said in a statement.  The JIM found that the Syrian government of Bashar al-Assad is to blame for a chemical attack on the opposition-held town of Khan Sheikhoun that killed dozens of people last April, according to a report sent to the United Nations Security Council last Thursday.  This unconscionable attack marks the fourth time that the JIM has confirmed that the Assad regime used chemical weapons, underscoring the brutal and horrifying barbarism of Bashar al-Assad and making the protection provided by Russia even more egregious,  the White House said.  JIM was unanimously created by the 15-member U.N. Security Council in 2015 and renewed in 2016 for another year. Its mandate is due to expire in mid-November.  The United States implores the UN Security Council to renew the mandate of the JIM so that we may continue to identify the perpetrators of these horrific attacks and send a clear message that the use of chemical weapons will not be tolerated,  the White House said.  In their 14th report since 2011, U.N. investigators said they had in all documented 33 chemical weapons attacks to date. Twenty-seven were by the government of President Bashar al-Assad, including seven between March 1 to July 7. Perpetrators had not been identified yet in six attacks, they said. The Assad government has repeatedly denied using chemical weapons. It said its strikes in Khan Sheikhoun hit a weapons depot belonging to rebel forces, a claim  excluded  by U.N. Commission of Inquiry on Syria chairman Paulo Pinheiro. That attack led U.S. President Donald Trump to launch the first U.S. air strikes on a Syrian air base. 