This is stated in a statement published on the Israeli troops on Twitter.

“Regarding the reporting of sirens ... three shells were fired from the Gaza Strip towards Israel,” the army press service said.

בהמשך לדיווח על התרעה, זוהו שלושה שיגורים משטח רצועת עזה לשטח ישראל

- צבא ההגנה לישראל (@idfonline) February 4, 2020

It was previously reported that air raid sirens worked in Israel.