A deadly sarin attack on a rebel-held area in April previous year prompted Trump to order a missile strike on the Shayrat air base, from which the Syrian operation is said to have been launched.
If necessary, the Trump administration is prepared to take military action against Syrian government forces to deter the use of chemical weapons, senior US officials said on Thursday.
"We take the allegations of chemical weapons use very seriously and are working with our partners on the ground to investigate the reports", State Department spokeswoman Heather Nauert told reporters.
"These attacks constitute clear violations of worldwide humanitarian law and the Convention on Chemical Weapons", the report says.
Characteristics of some of those recent attacks suggest that Syria may be developing new weapons and methods for delivering poison chemicals, possibly to make it harder to trace their origin, the officials said, speaking on condition of anonymity, but they declined to provide specifics.
He accused Russia of violating its own commitments under a 2013 US-Russia agreement to rid Syria of its chemical weapons stockpiles and an global treaty that bars their use.
The officials also noted that Syria's government isn't the only chemical weapons threat in the region.
United States designates Hamas leader as terrorist
Hamas, which dominates the Gaza Strip, is already designated a terrorist group by the US, Israel, the European Union and UK. The State Department's statement explicitly accused Haniyeh of involvement in terror attacks against Israelis.
A Civil Defence member carries a damaged canister in Ibleen village from what activists said was a chlorine gas attack, on Kansafra, Ibleen and Josef villages, Idlib countryside May 3, 2015.
The bloodshed came a day after the latest suspected chlorine attack by the regime of President Bashar al-Assad on Ghouta, which has been besieged by government forces since 2013.
"We are even more concerned about the possibility of sarin use, and we are looking for the evidence", he said. Nearly all independent analysts and investigators agree the Syrian regime is the culprit of the chemical attacks.
Rebel forces have been fighting Assad in a gruesome civil war for years.
Long-time ally Russian Federation has also rejected claims about the use of chemical weapons by the Syrian regime and called into question the results of the OCPW inquiries.
The senior US officials, speaking to journalists on the condition of anonymity because they were not authorized to speak publicly, said there did not appear to have been any "large use" of banned munitions since April.
A war monitor said at least 20 civilians were killed in Syrian government air strikes on rebel-held territory in the country's north on Thursday and three children were killed in artillery strikes on Eastern Ghouta.