Let p>3 be a prime, and let d∈Z with p∤d. For the determinants Sm(d,p)=det[(i2+dj2)m]1⩽i,j⩽(p−1)/2 (2p−1⩽m⩽p−1), Sun recently determined Sm(d,p) modulo p when m∈{p−2,p−3} and (p−d)=−1. In this paper, we obtain Sp−2(d,p) modulo p in the remaining case (p−d)=1, and determine the Legendre symbols (pSp−3(d,p)) and (pSp−4(d,p)) in some special cases.